1. Field of the Invention
The present invention relates to a ballast for supplying a plurality of discharge lamps.
2. Description of Related Art
Discharge lamps, like fluorescent lamps, require a supply ballast that generates the operational voltage needed for the operation of the discharge lamps from the mains voltage, and which, moreover, allows the ignition of the discharge lamps and, possibly, the preheating of the lamp electrodes.
Normally, each discharge lamp has its own ballast. However, ballasts are known that can operate a plurality of discharge lamps simultaneously. Such ballasts have an operational member, wherein each discharge lamp has its own respective lamp circuit containing electrode terminals between which the lamp is inserted. In addition, a separate inductance is provided for each lamp, which generates the high voltages necessary for the ignition of the lamp during the ignition phase.
Ballasts that are designed for the simultaneous operation of a plurality of discharge lamps, however, can only be operated such that all connected discharge lamps are either on or off. Thus, it is not possible to turn an individual discharge lamp or a group discharge lamps on or off independently from the other discharge lamps connected to the ballast.
It is an object of the present invention to provide a ballast that allows individual discharge lamps and groups of discharge lamps to be turned on and off separately, without thereby influencing the remaining discharge lamps operated by the ballast.